The present invention relates to a process for preparing an aminomethylphosphonic chelating resin by amination, hydrolysis and methylphosphonation of haloalkylated polymer beads. Aminomethylphosphonic chelating resins are for example useful for removing multivalent, alkaline earth metal cations such as calcium ions or heavy metal cations such as copper ions from salt solutions.
Processes for preparing aminomethylphosphonic chelating resins and resins containing similar functional groups are generally known. British Patent 2 040 950 and French patent application 2 442 859 disclose a method of producing ion exchange resins containing (aminomethyl)(hydroxymethyl)phosphinic acid groups by aminating chloromethylated copolymers of styrene and divinylbenzene, for example with ethylene diamine or monoethanolamine. Hexamethylenetetramine is also suggested as an aminating agent for producing polyvinylbenzylamine. The aminated copolymers are then treated with formalin or another source of formaldehyde and with a salt of hyphosphorous acid in an acidic medium.
British patent 859,834 discloses amphoteric ion-exchange resins comprising a polymeric substituted-aminomethyl phosphonate which are produced by reacting a dialkyl or diaryl hydrogen phosphonate with a mixture of a phenol-formaldehyde condensate polymer and a primary or secondary amine and then partially hydrolysing the product.
Amine- and phosphonate containing polymers are produced according to Chemical Abstracts, vol 99, no. 12 September 1983, page 35, abstract no. 89074s by reacting a chloromethylated divinylbenzene-styrene copolymer with sodium carbonate to produce a copolymer having -CHO groups and reacting the produced aldehyde copolymer with ammonia or a primary amine and then with H.sub.3 PO.sub.3.
According to Chemical Abstracts, vol 98, no. 22, May 1983, page 33, Abstract no 180408u resins containing aminomethylphosphonic groups are produced by reacting aminomethylated divinylbenzene-styrene copolymers with formaldehyde and then with phosphorous acid. In Chemical Abstracts, vol 80, no. 16, April 1974, page 28, abstract no. 83990y a similar method is described, however the phosphorous acid and formaldehyde are premixed and hexamethylenetetramine is used for aminating chloromethylated divinylbenzene-styrene copolymers.
European patent application 0 065 120 suggests reacting an amino resin having amine-reactive groups with an amino compound to produce an aminated resin and subsequently reacting the produced aminated resin with an alkylphosphonation agent in a known way, for example with formaldehyde and a phosphonation agent such as phosphorous acid or phosphorous trichloride.
European patent application 87934 discloses macroporous alkylamino phosphonic chelating resins and a process for preparing them. In the described process a reticulated vinylaromatic macroporous matrix is prepared and aminophosphonic functional groups are successively introduced by effecting the steps of chloromethylation, amination, hydrolysis and alkylphosphonation. The chloromethylation of a styrenedivinylbenzene matrix is carried out with a mixture of formaldehyde and methanol. The mixture is heated for 4 hours and then neutralised with sodium hydroxide. The chloromethylated copolymer beads are washed. The amination is then carried out with a mixture of methylal and hexamethylene tetramine or with other nitrogenous compounds. The reaction takes 6 hours. The beads are dried and then washed until complete disappearance of the traces of amine and methylal. The hydrolysis is then carried out by contacting the aminated resin beads with hydrochloric acid during 4 hours at 45.degree. C. The hydrolysed beads are then dried and washed until neutrality. These beads are then subjected to alkylphosphonation by contacting them with phosphorous acid or another phosphonation agent, formaldehyde and hydrochloric acid for 3 hours. Unfortunately, these repeated purification and drying steps are time-consuming, consume much energy and produce an undesirable amount of waste water.
U.S. Pat. No. 4,002,564 basically suggests the same process for preparing cation-exchange resins having a gel-type or macroporous matrix and aminomethylphosphonic groups as European patent application 87,934. In U.S. Pat. No. 4,002,564 phosphorous trihalide is suggested as a phosphonating agent.
Accordingly, one object of the present invention is to provide a new process for preparing aminomethylphosphonic chelating resins. Another object of the present invention to provide a process for preparing aminomethylphosphonic chelating resins wherein less waste producing purification and drying steps are necessary.